Molecular Models for III-V Quantum Dots

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Quantum dots (QDs) are fragments of semiconductors that absorb and emit different colours of light depending on their size. They are a nanoscale device, that is they are over a million times smaller than a golf ball. Quantum dots have excellent properties that offer the potential for widespread applications ranging from solar panels to biological and medical sensing and from use in television screens to electronics. However, the major barrier to their industrial uptake is their challenging manufacture. In an ideal preparation of these nanoparticles, all of the output quantum dots would be identical in size - representing perfect quality control. In practice however, this is very difficult to achieve. In a standard method, two materials react to form a central point, or nucleus, around which the QD grows in a matter of minutes. If there is non-even mixing of the precursors, then these nuclei form at different times and so the growth period lasts for different lengths of time, resulting in different sizes. In a research laboratory it is relatively easy to control this, but on a practical industrial scale, it extremely hard to achieve instantaneous mixing. This has resulted in a low uptake of the use and manufacture of these amazing materials. In this project, we will develop a new synthetic route that eliminates the need to form nuclei, by preparing these in advance - removing the need for instantaneous mixing. This will enable us to have perfect quality control over the size of the quantum dots that we produce. We will prepare compounds, consisting of a cluster of the elements that make up the quantum dot and optimise the route from these cluster nuclei to QDs by controlling the growth.A secondary advantage of these clusters is that they will have the same atomic structure as the QDs. For quantum dots it can be very hard to determine the exact position of each atom, without using an extremely expensive high-powered electron microscopes, of which there are only a few worldwide. However, we can take advantage of routine molecular techniques to determine the exact atomic positions of the cluster's constituents, such as any additives or their surfaces. In this second part of the project, we will develop so-called molecular models of the QDs, to allow the rationale design of future materials and empower more researchers, facilitating the future development of QDs.